1. Field of the Invention
This invention pertains generally to antennas and, more particularly, to antennas for application in an environment subjected to a voltage potential where breakdown can occur. The invention also pertains to such antennas for application with sensors or switchgear devices.
2. Background Information
Diagnostic sensors that are located on the line or “high” voltage side of switchgear devices, such as circuit breakers, and/or on the bus structure of such devices must survive impulse voltage tests (e.g., rated lightning impulse voltage; BIL (Basic Impulse Level)) to prove that arcing between conductive surfaces does not occur. Survival of these tests is dependent upon the distance between the conductive surfaces, the rated breakdown of the material between those surfaces, the geometry of those surfaces and the applied voltage potential.
If such a diagnostic sensor might implement, for example, communications employing an antenna, then such antenna, if located outside of the package of the diagnostic sensor, may likely be subjected to arcing during the impulse voltage tests.
U.S. Pat. No. 4,725,449 discloses that problems have been encountered with radio frequency (RF) ion source antenna coils. When the antenna coil is made of bare metal, such as copper, sparking or arcing may occur in a vacuum chamber, both between the turns of the coil, and also between the coil and various electrodes which may be employed in the ion source. When the antenna coil is operated at high power levels, the RF voltage between different portions of the coil may be quite high. This patent further discloses an RF ion source antenna coil coated with a thin impervious layer or coating of glass which is fused to a metal conductor and is strongly adherent thereto. The glass coating covers the entire surface of the antenna conductor, but not including the terminal portions or contacts, which are left bare. The glass coating is thin, continuous, impervious and substantially uniform in thickness. The continuous, impervious glass coating is an excellent electrical insulator and is resistant to voltage breakdown. The patent also discloses that the glass coating will withstand a voltage of five kV.
There is room for improvement in antennas. There is also room for improvement in sensors and switchgear devices employing an antenna.